γ-Globin Gene Expression in Chemical Inducer of Dimerization (CID)-dependent Multipotential Cells Established from Human β-Globin Locus Yeast Artificial Chromosome (β-YAC) Transgenic Mice

Identification of trans-acting factors or drugs capable of reactivating γ-globin gene expression is complicated by the lack of suitable cell lines. Human K562 cells co-express ϵ- and γ-globin but not β-globin; transgenic mouse erythroleukemia 585 cells express predominantly human β-globin but also γ-globin; and transgenic murine GM979 cells co-express human γ-and β-globin. Human β-globin locus yeast artificial chromosome transgenic mice display correct developmental regulation of β-like globin gene expression. We rationalized that cells established from the adult bone marrow of these mice might express exclusively β-globin and therefore could be employed to select or screen inducers of γ-globin expression. A thrombopoietin receptor derivative that brings the proliferative status of primary mouse bone marrow cells under control of a chemical inducer of dimerization was employed to institute and maintain these cell populations. Human β-globin was expressed, but γ-globin was not; a similar expression pattern was observed in cells derived from fetal liver. γ-Globin expression was induced upon exposure to 5-azacytidine, in cells derived from –117 Greek hereditary persistence of fetal hemoglobin human β-globin locus yeast artificial chromosome (β-YAC) mice, showing that the hereditary persistence of fetal hemoglobin (HPFH) phenotype was maintained in these cells or was reactivated by an artificial zinc finger-γ-globin transcription factor and the previously identified fetal globin transactivators fetal Krüppel-like factor (FKLF) and fetal globin-increasing factor (FGIF). These cells may be useful for identifying transcription factors that reactivate γ-globin synthesis or screening γ-globin inducers for the treatment of sickle cell disease or β-thalassemia.